Acinectobacter baumannii is a medically relevant opportunistic pathogen accounting for approximately 2 % of all healthcare associated infections in the United States. Sequence analysis of the A. baumannii genome revealed the presence of a 256 amino acid SurE ortholog which was expressed in E. coli and purified by nickel-affinity column chromatography. Polyacrylamide gel electrophoresis of recombinant SurE indicated a single Coomassie Blue staining band of approximately 26 kDa. Proteomic analysis corroborated the identity and molecular mass (27,488 Da) from the deduced sequence. Initial characterization using the artificial substrate pNPP indicated maximal phosphohydrolase activity at pH 5.5 in the presence of Mn2+ cation. Phosphate was also removed to varying degree from phosphorylated sugars, metabolites, amino acid and peptide derivatives. The SurE ortholog also exhibited 5’-nucleotidase activity removing phosphate from nucleotides AMP, CMP, IMP, UMP, dUPM, and TTP. kcat/Km values revealed UMP as the best nucleotide substrate. In summary, the SurE ortholog is a phosphatase with broad substrate specificity, the physiological significance of which remains to be established in A. baumannii.
Author(s): Phuong Cao, Jieh-Juen Yu, Bernard P. Arulanandam, Luke T. Daum, Robert Renthal, and James P. Chambers